Previous research in our laboratory has indicated that pregnant women who smoke expose themselves and their placentas to increased levels of cadmium (Cd); the levels observed were 56 and 32% higher in whole blood and placental tissue, respectively. Previous research on pregnant animals has shown that a metabolic interaction occurs between Cd and zinc (Zn) which may result in the fetus receiving less Zn; Zn is required for normal growth and development. If this interaction occurs in pregnant women, it may be heightened by the fact that Zn status normally decreases during pregnancy. Low Zn status alone has been associated with pregnancy complications and low birth weight infants. Thus, this study was designed to test the hypothesis that the increased Cd level in pregnant women who smoke alters the metabolism of Zn in the maternal - fetal placental unit, which may contribute to low birth weight infants. Zn status of the mothers and infants will be evaluated using plasma and red cell Zn levels, and serum alkaline phosphatase activity. The levels of Zn and alkaline phosphatase will also be measured in the placenta. Cd exposure will be evaluated by determining the levels of Cd in maternal blood and placental tissue, and by determining metallothionein levels in the placenta. To evaluate whether Cd exposure due to smoking affects Zn metabolism, various biochemical and clinical parameters of two population groups - smokers and nonsmokers - will be compared. Serum thiocyanate levels will be used to classify patients as smokers and nonsmokers. This study will provide basic knowledge concerning the interaction of Cd with Zn during pregnancy, and may provide evidence that Cd exposure thru cigarette smoking contributes to lower infant birth weight.